Device for recovering feebly magnetic material in wet separators



Oct; 10, 1967 w. N. LUNDMARK 3,346,113 DEVICE FOR RECOVERING FEEBLY MAGNETIC MATERIAL IN WET SEPARATORS Filed Jan. 10, 1966 BY f MW United States Patent O ABSTRACT OF THE DISCLOSURE A mgnetic wet separator comprises a drum rotatable about a horizontal shaft above but partially submerged in a water trough, with relatively strong magnets acting on a sub-merged portion of the drum and relatively weak magnets acting on an emergent portion of the drum. The poles of the magnets of both banks are of opposite polarity, and the provision of a relatively large number of weak magnets in the subsequent bank enables the attracted material to be tumbled a large number of times during washing out of the semi-grain.

The invention relates to an arrangement in magnetic wet separators for granular or powdered ore and similar material to be separated which separators comprise a drum rotatable about a horizontal shaft and having a non-mangetic circumferential wall, and stationary magnets disposed within said drum and adapted to lift the magnetic material out of a slurry of magnetic and nonmagnetic materials. The purpose of this arrangement is to render possible effective washing of the magnetic material lifted out of the water so as to obtain a concentrate as pure as possible. However, it has proved that in spite of the washing operation the concentrate is accompanied by some non-magnetic material, namely, particles or grain composed of magnetic material and gangue and usually termed semi-grain.

The object of the present invention is to devise a magnetic Wet separator in such a manner that the semigrain, too, can be separated out from the material so that the concentrate will be free of non-magnetic material. In a magnetic wet separator of the kind to which the invention relates there are stationary magnet banks disposed within the drum, the magnetic poles of one bank being located along that par-t of the circumference of the drum that submerges below the water level in a trough disposed below the drum, whereas the poles of another bank are located along a subsequent part of the circumference of the drum which subsequent part is positioned above the water level. In its broadest aspect the invention is characterized in that the poles of the last named bank which create a weaker magnetic field than the magnets of the first named bank are more closely spaced than the poles of the first named bank, that the trough has an outlet for so called semi-grain below the more closely spaced magnets, and that means are provided for washing material that travels with the drum and is lifted out of the water. Thereby it is possible to Wash semi-grain away from the concentrate and to discharge it through its outlet.

Advantageously the magnets of one bank are magnetically insulated from the magnets of the other bank, resulting in an increase of the field strength of the strong magnets the purpose of which is to attract the magnetic material in the water so that this material is moved to the circumferential wall of the drum and can travel therewith, The strength of the magnetic field created by the strong magnets can be further increased if the last 3,346,1 l3 Patented Oct. 10, 1967 magnet 0f the bank of strong magnets is of the same polarity as the first magnet of the bank of weak magnets. For the rest, successive magnets of each bank are advantageously of opposite polarity resulting in an improved separation.

Two embodiments of the invention are described hereinbelow with reference to the annexed drawing. FIG. 1 is a vertical sectional view at right angles to the shaft of the drum of a concurrent separator devised in accordance with the invention, and FIG. 2 is a similar view of a counter flow separator.

The term concurrent separator refers to a separator in which the tailings of the material to be separated are moving in the direction of rotation of the drum, and the term counter flow separator refers to a separator in which the tailings are moving counter to the direction of rotation.

Referring to the drawing, reference numeral 1 denotes the circumferential wall of a non-magnetic separator drum adapted to be driven such as to rotate about a horizontal shaft 2 in the direction indicated by an arrow 3. Below the drum there is provided a trough 4 which is continuously supplied with water and provided with a weir 6 for maintaining a water level 5 the position of which can be adjusted by lifting or lowering the weir. The lower part of the circumferential wall 1 of the drum submerges in the water below the level 5. On the side of the wall of the drum that moves downwards during rotation the trough has a sloping bottom which downwardly defines an inlet part 7 into which ore crushed to granular or powdered state or similar material to be separated is supplied together with water. The lowermost part of the trough has a discharge slot 8 for non-magnetic material which sinks through the slot, and is collected in an underlying pocket 9 having an outlet 10. On the side of the wall of the drum that moves out of the water the bottom of the trough extends upwards concentrically with the wall of the drum to a place slightly below a horizontal plane through the shaft 2 of the drum where the bottom of the trough is in the form of a threshold over which separated magnetic material, i.e. concentrate, is discharged into an outlet hopper 12 having an outlet 13. Below the outlet 13 there is provided an outlet 13 for middlings substantially consisting of so-called semi-grain composed of magnetic material and gangue.

Disposed within the drum there is a plurality of stationary magnets, namely, a bank of comparatively large and strong magnets 14, 15 having their poles at the part of the drum that submerges in the water, and a bank of smaller and weaker and more closely spaced magnets 16 on the side of the wall of the drum that moves out of the water above the water level 5. The purpose of the strong magnets is in the usual manner to attract the magnetic material to the outside of the drum so that the material can be lifted out of the water and delivered at the threshold 11. The purpose of the weaker magnets 16 is to hold the magnetic material on the wall of the drum so that this material travels with the drum up to and beyond the threshold 11 while the material is washed by water supplied between the threshold and the wall of the drum as indicated by an arrow 17. The material that travels with the wall of the drum contains not only concentrate, but also feebly magnetic material in the form of semi-grain. The last named material is held on the wall of the drum by comparatively feeble forces exerted by the weak magnets 16. Consequently, this material can be easily Washed away and separated from the concentrate by means of the washing water represented by the arrow 17. The washed away feebly magnetic material is discharged through the outlet 13.

Due to the fact that the weak magnets 16 are of small dimensions and relatively closely spaced more such magnets can be placed within a given angular range than 1n the case of the provision of stronger magnets of the same sizes as the magnets 14 and 15. The bristle-like accumulations 18, 19 and 20 formed by the material opposite the poles facilitate separation of non-magnetic material and flushing away of semi-grain. During the movement of a certain part of the wall of the drum past a magnet pole there is formed such an accumulation of magnetic material which is turned over on the wall of the drum if the next following magnet is of opposite polarity as compared with the first named magnet. Consequently, if the magnet 14 has a South pole close to the wall of the drum the magnet 15 should have a corresponding North pole. However, the next following weak magnet 16 should be of the same polarity as the magnet 15 and therefore should have a North pole at the wall of the drum. This improves the possibility of separating semi-grain by washing. An improved separation and recovering of pure concentrate is also rendered possible if the magnets 16 are magnetically insulated from the magnets 14 and 15.

In the embodiment of a counter flow separator illustrated in FIG. 2 the material to be separated is fed into a pocket 7' which through a separate duct communicates with an inlet 21 which as viewed in the direction of rotation 3 is located somewhat behind the lowermost point of the drum. The tailings or nn-magnetic materials are carried by the stream of water from the inlet 21 counter to the direction of rotation of the drum as in dicated by arrows 22. They are collected in a pocket or groove 23 and discharged through the outlet for tailings. The magnetic material travels with the drum, and semi-grain is flushed away by washing means 17 and is discharged through an outlet 13, whereas the concentrate moves upwards past the threshold 11 and is dis charged through the outlet 13.

According to FIG. 2 the weak magnets 16 are mounted on a holder 24 of non-magnetic material so as to be magnetically insulated from the strong magnets 14, 15.

What I-claim is:

1. A magnetic wet separator for granular or powered ore and similar material to be separated, comprising a drum rotatable about a horizontal shaft and having a non-magnetic circumferential wall, a trough disposed below the drum and means defining a water level in said trough, part of the circumference of the drum submerging below said water level stationary magnet banks disposed within said drum, the magnetic poles of one bank being located along that part of the circumference of the drum that submerges below the water level in said trough, whereas the poles of another bank are located along a subsequent part of the circumference of the drum which subsequent part is positioned above the water level, the poles of the last named bank being successively of opposite polarity and creating a weaker magnetic field than the magnets of the first named bank and being more closely spaced than the poles of the first named bank, the trough having an outlet for so-called semi-grain below the more closely spaced magnets, and means provided for washing material that travels with the drum and is lifted out of the water, whereby to wash semi-grain away from the concentrate and to discharge it through said outlet.

2. An apparatus as claimed in claim 1, characterized in that the magnets of one bank are magnetically insulated from the magnets of the other bank.

3. An apparatus as claimed in claim 1, characterized in that successive magnets of the bank of strong magnets are of opposite polarity, but that the last magnet of the bank of strong magnets is of the same polarity as the first magnet of the bank of weak magnets.

References Cited UNITED STATES PATENTS 2,003,430 6 /1935 Crockett 209-232 2,692,678 10/ 1954 Blind 209-223 2,945,590 7/ 1960 Stearns 209-223 2,992,737 7/1961 Buus 209-223 SAMIH N. ZAHARNA, Primary Examiner. F. MEDLEY, Assistant Examiner. 

1. A MAGNETIC WET SEPARATOR FOR GRANULAR OR POWERED ORE AND SIMILAR MATERIAL TO BE SEPARATED, COMPRISING A DRUM ROTATABLE ABOUT A HORIZONTAL SHAFT AND HAVING A NON-MAGNETIC CIRCUMFERENTIAL WALL, A TROUGH DISPOSED BELOW THE DRUM AND MEANS DEFINING A WATER LEVEL IN SAID TROUGH, PART OF THE CIRCUMFERENCE OF THE DRUM SUBMERGING BELOW SAID WATER LEVEL STATIONARY MAGNET BANKS DISPOSED WITHIN SAID DRUM, THE MAGNETIC POLES OF ONE BANK BEING LOCATED ALONG THAT PART OF THE CIRCUMFERENCE OF THE DRUM THAT SUBMERGES BELOW THE WATER LEVEL IN SAID TROUGH, WHEREAS THE POLES OF ANOTHER BANK ARE LOCATED ALONG A SUBSEQUENT PART OF THE CIRCUMFERENCE OF THE DRUM WHICH SUBSEQUENT PART IS POSITIONED ABOVE THE WATER LEVEL, THE POLES OF THE LAST NAMED BANK BEING SUCCESSIVELY OF OPPOSITE POLARITY AND CREATING A WEAKER MAGNETIC FIELD THAN THE MAGNETS OF THE FIRST NAMED BANK, THE CLOSELY SPACED THAN THE POLES OF THE FIRST NAMED BANK, THE TROUGH HAVING AN OUTLET FOR SO-CALLED SEMI-GRAIN BELOW THE MOR CLOSELY SPACE MAGNETS, AND MEANS PROVIDED FOR WASHING MATERIAL THAT TRAVESL WITH THE DRUM AND IS LIFTED OUT OF THE WATER, WHEREBY TO WASY SEMI-GRAIN AWAY FROM THE CONCENTRATE AND TO DISCHARGE IT THROUGH SAID OUTLET. 